asp.net core 發送QQ郵件

.netframework 中發送郵件的api主要是使用SmtpClient 類，到了.netcore,官方並不推薦使用SmtpClient API，詳情可查看官方說明:https://docs.microsoft.com/en-us/dotnet/api/system.net.mail.smtpclient?view=net-5.0,因此這里我使用第三方郵件發送庫：MailKit 來進行郵件的發送。

配置QQ郵箱

• 登錄QQ郵箱，選擇設置->賬戶->POP3/IMAP/SMTP/Exchange/CardDAV/CalDAV服務
  
  開啟POP3/SMTP服務以及IMAP/SMTP服務。

POP3服務開啟流程
1.開啟POP3服務![]
(https://www.lovecoding.com.cn:99//5596824483738550145.png)

2.POP3服務開啟成功后如下圖所示，會彈出一個框，注意：不是用這個框里的密碼進行發送郵件

3.生成用於發送郵件的授權碼

IMAP服務開啟流程
開啟流程和POP3開啟流程類似。

創建郵件發送接口

• 安裝nuget包MailKit
• 添加IMailService接口

  using System;
  using System.Collections.Generic;
  using System.Text;
  using System.Threading.Tasks;
  
  namespace CommonLib.Email
  {
  	public interface IMailService
  	{
  		Task SendEmailAsync(MailRequest mailRequest);
  	}
  }
  

• 創建郵件信息相關實體類

  using Microsoft.AspNetCore.Http;
  using System;
  using System.Collections.Generic;
  using System.Text;
  namespace CommonLib.Email
  {
  	public class MailRequest
  	{
  		//收件地址
  		public string ToEmail { get; set; }
  		//郵件標題
  		public string Subject { get; set; }
  		//郵件內容,支持html
  		public string Body { get; set; }
  		//要發送的附件
  		public List<IFormFile> Attachments { get; set; }
  	}
  }
  

• 創建郵箱配置信息實體類

  using System;
  using System.Collections.Generic;
  using System.Text;
  namespace CommonLib.Email
  {
  	public class MailSettings
  	{
  		//用於發送郵件的郵箱賬號
  		public string Mail { get; set; }
  		//顯示名稱
  		public string DisplayName { get; set; }
  		//用於發送郵件的郵箱賬號的授權碼
  		public string Password { get; set; }
  		//用於發送郵件的郵箱服務器,QQ郵箱是：smtp.qq.com
  		public string Host { get; set; }
  		//用於發送郵件的郵箱服務器端口,QQ郵箱的端口是25
  		public int Port { get; set; }
  	}
  }
  

• 創建實現具體郵件發送邏輯的類,並實現IMailService接口

  using MailKit.Net.Smtp;
  using MailKit.Security;
  using Microsoft.Extensions.Options;
  using MimeKit;
  using System;
  using System.Collections.Generic;
  using System.IO;
  using System.Text;
  using System.Threading.Tasks;
  namespace CommonLib.Email
  {
  	public class MailService : IMailService
  	{
  		private readonly MailSettings _mailSettings;
  		public MailService(IOptions<MailSettings> mailSettings)
  		{
  			_mailSettings = mailSettings.Value;
  			//這里這個密碼是QQ郵箱授權碼
  			_mailSettings.Password = mailSettings.Value.Password;
  		}
  		public async Task SendEmailAsync(MailRequest mailRequest)
  		{
  			var email = new MimeMessage();
  			//一定要使用下面這句代碼添加發送人郵箱信息,否則QQ收件箱那邊無法看到發送人的郵箱信息。
  			email.From.Add(MailboxAddress.Parse(_mailSettings.Mail));
  			email.Sender = MailboxAddress.Parse(_mailSettings.Mail);
  			email.To.Add(MailboxAddress.Parse(mailRequest.ToEmail));
  			email.Subject = mailRequest.Subject;
  			var builder = new BodyBuilder();
  			if (mailRequest.Attachments != null)
  			{
  				byte[] fileBytes;
  				foreach (var file in mailRequest.Attachments)
  				{
  					if (file.Length > 0)
  					{
  						using (var ms = new MemoryStream())
  						{
  							file.CopyTo(ms);
  							fileBytes = ms.ToArray();
  						}
  						builder.Attachments.Add(file.FileName, fileBytes, MimeKit.ContentType.Parse(file.ContentType));
  					}
  				}
  			}
  			builder.HtmlBody = mailRequest.Body;
  			email.Body = builder.ToMessageBody();
  			using (var smtp = new SmtpClient())
  			{
  				smtp.Connect(_mailSettings.Host, _mailSettings.Port, SecureSocketOptions.StartTls);
  				smtp.Authenticate(_mailSettings.Mail, _mailSettings.Password);
  				await smtp.SendAsync(email);
  				smtp.Disconnect(true);
  			}
  		}
  	}
  }
  

打開appsettings.Development.json文件，加入發送郵件所用到的郵箱賬號、郵箱服務器等信息。

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "MailSettings": {
    "Mail": "[e-mail]",
    "DisplayName": "陳新",
    "Password": "xxx",
    "Host": "smtp.qq.com",
    "Port": 25
  },
  "urls": "http://*:80"
}

到這里，基本配置工作已經完成，但是需要注意的是將代碼發布到雲服務器上（如騰訊雲）時需要注意解封25端口，否則無法正常發送郵件。

騰訊雲25端口開放方法請參見：https://cloud.tencent.com/document/product/213/40436